Screw press for mechanically separating liquids from mixtures of liquids and solids

Abstract

A screw press for extracting liquids from liquid-solid mixtures continuously and in a single operation. The press comprises a barrel divided into a feed section and a pin-barrel section. A rotatable screw is disposed in the barrel. Grooves are provided in the feed section to ensure a good feed input and hence an economical throughput, the pin-barrel section including radial pins extending into the barrel which, together with the rotation of the screw cause a high pressure to build up in the barrel thereby comminuting the mixture. The screw has helical flights formed thereon, the flights defining ridges, radial bores being formed in the ridges which communicate with an axial bore formed in the screw permitting the draining away the extracted liquid directly from the region in which it is extracted.

I claim: 
     
       1. A screw press for mechanically separating liquids from a solid-liquid mixture, comprising: (a) a cylindrical barrel,   (b) a rotatable screw mounted for rotation in said barrel, said screw having a base with an axial bore, and a helical flight and defining with said band a relatively low pressure feed zone in which material is fed through an inlet to the interior of the press, and a relatively high pressure pin-barrel mixing zone located downstream of said feed zone, said barrel being formed with internal grooves in said feed zone,   (c) filter means disposed opposite said inlet in said feed zone for removing extracted liquid from the mixture under said low pressure conditions,   (d) mixing pin means extending through said barrel in said pin-barrel mixing zone and being directed radially inward to a position adjacent the base of said screw, the helical flight of said screw being longitudinally interrupted in the area of said pin means to permit rotation of said screw, said helical flight in said mixing zone defining ridges closely adjacent the internal surface of said barrel so as to provide, in combination with said mixing pins, an area of high pressure, said ridges being formed with a plurality of radially inwardly directed bores which communicate with said axial bore in said screw to release the liquid extracted from the mixture under high pressure in the mixing zone,   (e) means for maintaining the high pressure in said mixing zone, and   (f) outlet means for the relatively dry solid product from which the liquid has been extracted.   
     
     
       2. Apparatus as recited in claim 1, wherein the direction of said grooves in said barrel in said feed zone either correspond to or is opposite from the direction of said helical flight means, the cross-section of said grooves being selected from square, rectangular and triangular. 
     
     
       3. Apparatus as recited in claim 1 wherein said mixing pin means are substantially equiangularly disposed around said barrel in longitudinally spaced pin planes, said mixing pin means being radially adjustable so as to vary the gap between said pins and the base of said screw, the portions of said mixing pin means extending into said barrel having a cross-section selected from round, quadrilateral and polygonal. 
     
     
       4. Apparatus as recited in claim 1 further including axially centrally divided filter ring means disposed intermediate said feed zone and said pin-barrel zone and connected thereto, said filter ring means defining a plurality of filter apertures disposed at regular intervals around said filter ring means. 
     
     
       5. Apparatus as recited in claim 4 wherein said barrel comprises a plurality of filter ring portions, said filter ring portions alternating with barrel portions not having filter apertures. 
     
     
       6. A device as recited in claim 4, wherein said filter apertures are conically shaped, with the circular cross-section at the outer end of each aperture being up to five times the diameter of said aperture at its radially inner end. 
     
     
       7. Apparatus as recited in claim 1, wherein said ridges of said helical flights are formed with grooves extending longitudinally in said ridges and communicating with said radial bores. 
     
     
       8. Apparatus as recited in claim 1, wherein said means for maintaining pressure in said mixing zone comprises a pressure-loaded cone means which opens said outlet when a preselected pressure is reached. 
     
     
       9. Apparatus as recited in claim 8, wherein said cone means is adapted to be driven and has an external surface defining additional grooves, the direction of said additional grooves being helical or axial. 
     
     
       10. Apparatus as recited in claim 1 wherein said barrel member and said screw, at least in said feed zone, taper conically inwardly in a direction of material conveyance and towards said mixing zone of said barrel. 
     
     
       11. Apparatus as recited in claim 1, wherein said barrel member and said screw are disposed vertically, and further including filter ring means, said filter ring positioned between said feed zone and said pin-barrel zone. 
     
     
       12. The apparatus of claim 11, wherein said means for maintaining the high pressure in said mixing zone comprises an increased diameter screw base adjacent said outlet means, consequently substantially reducing the space between said base and said barrel and correspondingly increasing and maintaining the higher pressure in said mixing zone. 
     
     
       13. The apparatus of claim 1, wherein said means for maintaining the high pressure in said mixing zone comprises an increased diameter screw base adjacent said outlet means, consequently substantially reducing the space between said base and said barrel and correspondingly increasing and maintaining the higher pressure in said mixing zone.